public.proto

/**
Public API

The Transiter public API is based around hierarchal resources, like many REST APIs.
This is the resource hierarchy:

```
System
 |- Agency
 |- Alert
 |- Feed
 |   |- Feed update
 |- Route
 |   |- Trip
 |       |- Vehicle with no ID
 |- Stop
 |- Transfer
 |- Vehicle with ID
```

For each resource there is a proto message type, a list endpoint, and a get endpoints.
For stops, the message is [Stop](#stop), the list endpoint is [ListStops], and the get endpoint is [GetStop].

The URLs in the HTTP API are determined by the hierarchy; thus:

- List all systems has URL `/systems`,
- Get system with ID `<system_id>` has URL `/systems/<system_id>`,
- List all routes in the system has URL `/systems/<system_id>/routes`,
- Get route has URL `/systems/<system_id>/routes/<route_id>`,

and so on.

Many resources refer to other resources across the hierarchy.
For example, each route has an agency it is attached to.
Each stop has a list of service maps, each of which contains a set of routes.
In these situations the resource message contains a _reference_ to the other resource.
The [Route](#route) message contains an agency reference, in the form of an [Agency.Reference](#agencyreference)
  message.
These reference messages contain at least enough information to uniquely identify the resource.
However they also contain additional information that is considered generally useful;
  thus, the [Stop.Reference](#stopreference) message contains the stop's name.
What counts as "considered generally" is obviously very subjective and open to change.

The following table summarizes all of the resources and their types.
The right-most column describes the source_of the resource.
The public API is a read-only API so all of the resources come from somewhere else.

| Resource    | Reference type | List endpoint | Get endpoint | Source |
| ----------- | --------------- | ---------- | ------------------ | -------|
| [Agency](#agency)   | [Agency.Reference](#agencyreference) | [GetAgency] | [ListAgency]  | GTFS static
| Alert       | System          | [Alert]    | [Alert.Reference]    | GTFS realtime
| Feed        | System          |            |                    | system config
| Feed update | Feed            |            |                    | Transiter update process
| Route       | System          |            |                    | GTFS static
| Trip        | Route           |            |                    | GTFS realtime
| Stop        | System          |            |                    | GTFS static
| System      | None            |            |                    | system config
| Transfer    | System          |            |                    | GTFS static
| Vehicle     | System or trip  |            |                    | GTFS realtime

*/
syntax = "proto3";

import "google/api/annotations.proto";

option go_package = "github.com/jamespfennell/transiter/api";

service Public {
  // API entrypoint
  //
  // `GET /`
  //
  // Provides basic information about this Transiter instance and the Transit systems it contains.
  rpc Entrypoint(EntrypointRequest) returns (EntrypointReply) {
    option (google.api.http) = {
      get: "/"
    };
  }

  // List systems
  //
  // `GET /systems`
  //
  // List all transit systems that are installed in this Transiter instance.
  rpc ListSystems(ListSystemsRequest) returns (ListSystemsReply) {
    option (google.api.http) = {
      get: "/systems"
    };
  }

  // Get system
  //
  // `GET /systems/<system_id>`
  //
  // Get a system by its ID.
  rpc GetSystem(GetSystemRequest) returns (System) {
    option (google.api.http) = {
      get: "/systems/{system_id}"
    };
  }

  // List agencies
  //
  // `GET /systems/<system_id>/agencies`
  //
  // List all agencies in a system.
  rpc ListAgencies(ListAgenciesRequest) returns (ListAgenciesReply) {
    option (google.api.http) = {
      get: "/systems/{system_id}/agencies"
    };
  }

  // Get agency
  //
  // `GET /systems/<system_id>/agencies/<agency_id>`
  //
  // Get an agency in a system by its ID.
  rpc GetAgency(GetAgencyRequest) returns (Agency) {
    option (google.api.http) = {
      get: "/systems/{system_id}/agencies/{agency_id}"
    };
  }

  // List stops
  //
  // `GET /systems/<system_id>/stops`
  //
  // List all stops in a system.
  //
  // This endpoint is paginated.
  // If there are more results, the `next_id` field of the response will be populated.
  // To get more results, make the same request with the `first_id` field set to the value of `next_id` in the response.
  rpc ListStops(ListStopsRequest) returns (ListStopsReply) {
    option (google.api.http) = {
      get: "/systems/{system_id}/stops"
    };
  }

  // Get stop
  //
  // `GET /systems/<system_id>/stops/<stop_id>`
  //
  // Get a stop in a system by its ID.
  rpc GetStop(GetStopRequest) returns (Stop) {
    option (google.api.http) = {
      get: "/systems/{system_id}/stops/{stop_id}"
    };
  }

  // List routes
  //
  // `GET /systems/<system_id>/routes`
  //
  // List all routes in a system.
  rpc ListRoutes(ListRoutesRequest) returns (ListRoutesReply) {
    option (google.api.http) = {
      get: "/systems/{system_id}/routes"
    };
  }

  // Get route
  //
  // `GET /systems/<system_id>/routes/<route_id>`
  //
  // Get a route in a system by its ID.
  rpc GetRoute(GetRouteRequest) returns (Route) {
    option (google.api.http) = {
      get: "/systems/{system_id}/routes/{route_id}"
    };
  }

  // List trips
  //
  // `GET /systems/<system_id>/routes/<route_id>/trips`
  //
  // List all trips in a route.
  rpc ListTrips(ListTripsRequest) returns (ListTripsReply) {
    option (google.api.http) = {
      get: "/systems/{system_id}/routes/{route_id}/trips"
    };
  }

  // Get trip
  //
  // `GET /systems/<system_id>/routes/<route_id>/trips/<trip_id>`
  //
  // Get a trip by its ID.
  rpc GetTrip(GetTripRequest) returns (Trip) {
    option (google.api.http) = {
      get: "/systems/{system_id}/routes/{route_id}/trips/{trip_id}"
    };
  }

  // List alerts
  //
  // `GET /systems/<system_id>/alerts`
  //
  // List all alerts in a system.
  // By default this endpoint returns both active alerts
  //   (alerts which have an active period containing the current time) and non-active alerts.
  rpc ListAlerts(ListAlertsRequest) returns (ListAlertsReply) {
    option (google.api.http) = {
      get: "/systems/{system_id}/alerts"
    };
  }

  // Get alert
  //
  // `GET /systems/<system_id>/alerts/<alert_id>`
  //
  // Get an alert by its ID.
  rpc GetAlert(GetAlertRequest) returns (Alert) {
    option (google.api.http) = {
      get: "/systems/{system_id}/alerts/{alert_id}"
    };
  }

  // List transfers
  //
  // `GET /systems/<system_id>/transfers`
  //
  // List all transfers in a system.
  rpc ListTransfers(ListTransfersRequest) returns (ListTransfersReply) {
    option (google.api.http) = {
      get: "/systems/{system_id}/transfers"
    };
  }

  // List feeds
  //
  // `GET /systems/<system_id>/feeds`
  //
  // List all feeds for a system.
  rpc ListFeeds(ListFeedsRequest) returns (ListFeedsReply) {
    option (google.api.http) = {
      get: "/systems/{system_id}/feeds"
    };
  }

  // Get feed
  //
  // `GET /systems/<system_id>/feeds/<feed_id>`
  //
  // Get a feed in a system by its ID.
  rpc GetFeed(GetFeedRequest) returns (Feed) {
    option (google.api.http) = {
      get: "/systems/{system_id}/feeds/{feed_id}"
    };
  }

  // List feed updates
  //
  // `GET /systems/<system_id>/feeds/<feed_id>/updates`
  //
  // List feeds updates for a feed.
  rpc ListFeedUpdates(ListFeedUpdatesRequest) returns (ListFeedUpdatesReply) {
    option (google.api.http) = {
      get: "/systems/{system_id}/feeds/{feed_id}/updates"
    };
  }
}

// Request payload for the entrypoint endpoint.
message EntrypointRequest {}

// Response payload for the entrypoint endpoint.
message EntrypointReply {
  // Message containing version information about a Transiter binary.
  message TransiterDetails {
    // The version of the Transiter binary this instance is running.
    string version = 1;
    // URL of the Transiter GitHub respository.
    string href = 2;

    // Message containing information about a specific Transiter CI build.
    message Build {
      // The GitHub build number.
      string number = 3;
      // Time the binary was built, in the form of a human readable string.
      string built_at = 4;
      // Time the binary was built, in the form of a Unix timestamp.
      string built_at_timestamp = 5;
      // Hash of the Git commit that the binary was built at.
      string git_commit_hash = 6;
      // URL of the GitHub actions CI run.
      string href = 7;
    }
    // Information about the CI build invocation that built this Transiter binary.
    optional Build build = 3;
  }
  // Version and other information about this Transiter binary.
  TransiterDetails transiter = 1;

  // Systems that are installed in this Transiter instance.
  ChildResources systems = 2;
}

// Request payload for the list systems endpoint.
message ListSystemsRequest {}

// Response payload for the list systems endpoint.
message ListSystemsReply {
  // List of systems.
  repeated System systems = 1;
}

// Request payload for the get system endpoint.
message GetSystemRequest {
  // ID of the system to get.
  //
  // This is a URL parameter in the HTTP API.
  string system_id = 1;
}

// Request payload for the list agencies endpoint.
message ListAgenciesRequest {
  // ID of the system for which to list agencies.
  //
  // This is a URL parameter in the HTTP API.
  string system_id = 1;
}

// Response payload for the list agencies endpoint.
message ListAgenciesReply {
  // List of agencies.
  repeated Agency agencies = 1;
}

// Request payload for the get agency endpoint.
message GetAgencyRequest {
  // ID of the system the agency is in.
  //
  // This is a URL parameter in the HTTP API.
  string system_id = 1;
  // ID of the agency.
  //
  // This is a URL parameter in the HTTP API.
  string agency_id = 2;
}

// Request payload for the list stops endpoint.
message ListStopsRequest {
  // ID of the system for which to list stops.
  //
  // This is a URL parameter in the HTTP API.
  string system_id = 1;

  // The possible search modes when listing stops.
  enum SearchMode {
    // Return a paginated list of stops sorted by stop ID.
    ID = 0;
    // Return all stops within max_distance of (latitude, longitude), sorted by the distance.
    DISTANCE = 1;
  }
  // The type of search to perform when listing stops.
  optional SearchMode search_mode = 13;

  // If true, only return stops whose IDs are specified in the repeated `id` field.
  // Only supported when the search mode is ID.
  bool only_return_specified_ids = 8;
  // IDs to return if `only_return_specified_ids` is set to true. It is an error to
  // populate this field if `only_return_specified_ids` is false.
  // Only supported when the search mode is ID.
  repeated string id = 9;
  // ID of the first stop to return. If not set, the stop with the smallest ID will be first.
  // Only supported when the search mode is ID.
  optional string first_id = 2;

  // Maximum number of stops to return.
  // This is supported in all search modes.
  // For performance reasons, if it is larger than 100 it is rounded down to 100.
  optional int32 limit = 3;

  // If true, the stop times field will not be populated.
  // This will generally make the response faster to generate.
  bool skip_stop_times = 4;
  // If true, the service maps field will not be populated.
  // This will generally make the response faster to generate.
  bool skip_service_maps = 5;
  // If true, the alerts field will not be populated.
  // This will generally make the response faster to generate.
  bool skip_alerts = 6;
  // If true, the transfers field will not be populated.
  // This will generally make the response faster to generate.
  bool skip_transfers = 7;

  // The maximum distance in kilometers that a stop must be from
  // latitude, longitude to be listed when using DISTANCE search mode.
  optional double max_distance = 10;

  // The latitude relative to the returned stops when using DISTANCE search mode.
  optional double latitude = 11;

  // The longitude relative to the returned stops when using DISTANCE search mode.
  optional double longitude = 12;
}

// Response payload for the list stops endpoint.
message ListStopsReply {
  // List of stops.
  repeated Stop stops = 1;

  // ID of the next stop to return, if there are more results.
  optional string next_id = 2;
}

// Reqeust payload for the get stop endpoint.
message GetStopRequest {
  // ID of the system the stop is in.
  //
  // This is a URL parameter in the HTTP API.
  string system_id = 1;
  // ID of the stop.
  //
  // This is a URL parameter in the HTTP API.
  string stop_id = 2;

  // If true, the stop times field will not be populated.
  // This will generally make the response faster to generate.
  bool skip_stop_times = 4;
  // If true, the service maps field will not be populated.
  // This will generally make the response faster to generate.
  bool skip_service_maps = 5;
  // If true, the alerts field will not be populated.
  // This will generally make the response faster to generate.
  bool skip_alerts = 6;
  // If true, the transfers field will not be populated.
  // This will generally make the response faster to generate.
  bool skip_transfers = 7;
}

// Request payload for the list routes endpoint.
message ListRoutesRequest {
  // ID of the system for which to list routes.
  //
  // This is a URL parameter in the HTTP API.
  string system_id = 1;

  // If true, the estimated headway fields will not be populated.
  // This will generally make the response faster to generate.
  bool skip_estimated_headways = 2;
  // If true, the service maps field will not be populated.
  // This will generally make the response faster to generate.
  bool skip_service_maps = 3;
  // If true, the alerts field will not be populated.
  // This will generally make the response faster to generate.
  bool skip_alerts = 4;
}

// Response payload for the list routes endpoint.
message ListRoutesReply {
  // List of routes.
  repeated Route routes = 1;
}

// Request payload for the get route endpoint.
message GetRouteRequest {
  // ID of the system the route is in.
  //
  // This is a URL parameter in the HTTP API.
  string system_id = 1;
  // ID of the route.
  //
  // This is a URL parameter in the HTTP API.
  string route_id = 2;

  // If true, the estimated headway field will not be populated.
  // This will generally make the response faster to generate.
  bool skip_estimated_headways = 3;
  // If true, the service maps field will not be populated.
  // This will generally make the response faster to generate.
  bool skip_service_maps = 4;
  // If true, the alerts field will not be populated.
  // This will generally make the response faster to generate.
  bool skip_alerts = 5;
}

// Request payload for the list trips endpoint.
message ListTripsRequest {
  // ID of the system the route is in.
  //
  // This is a URL parameter in the HTTP API.
  string system_id = 1;
  // ID of the route for which to list trips
  //
  // This is a URL parameter in the HTTP API.
  string route_id = 2;
}

// Response payload for the list trips endpoint.
message ListTripsReply {
  // List of trips.
  repeated Trip trips = 1;
}

// Request payload for the list alerts endpoint.
message ListAlertsRequest {
  // ID of the system for which to list alerts.
  //
  // This is a URL parameter in the HTTP API.
  string system_id = 1;

  // If non-empty, only alerts with the provided IDs are returned.
  // This is interpreted as a filtering condition, so it is not an error to provide non-existent IDs.
  //
  // If empty, all alerts in the system are returned.
  // TODO: add a boolean filter_on_alert_ids field
  repeated string alert_id = 2;
}

// Response payload for the list alerts endpoiont.
message ListAlertsReply {
  // List of alerts.
  repeated Alert alerts = 1;
}

// Request payload for the get alert endpoint.
message GetAlertRequest {
  // ID of the system the alert is in.
  //
  // This is a URL parameter in the HTTP API.
  string system_id = 1;
  // ID of the alert.
  //
  // This is a URL parameter in the HTTP API.
  string alert_id = 2;
}

// Request payload for the get trip endpoint.
message GetTripRequest {
  // ID of the system the trip is in.
  //
  // This is a URL parameter in the HTTP API.
  string system_id = 1;
  // ID of the route the trip is in.
  //
  // This is a URL parameter in the HTTP API.
  string route_id = 2;
  // ID of the route.
  //
  // This is a URL parameter in the HTTP API.
  string trip_id = 3;
}

// Request payload for the list feeds endpoint.
message ListFeedsRequest {
  // ID of the system for which to list feeds.
  string system_id = 1;
}

// Response payload for the list feeds endpoint.
message ListFeedsReply {
  // List of feeds.
  repeated Feed feeds = 1;
}

// Request payload for the list feed updates endpoint.
message ListFeedUpdatesRequest {
  // ID of the system the feed is in.
  //
  // This is a URL parameter in the HTTP API.
  string system_id = 1;
  // ID of the feed for which to list updates.
  //
  // This is a URL parameter in the HTTP API.
  string feed_id = 2;
}

// Response payload for the list feed updates endpoint.
message ListFeedUpdatesReply {
  // List of updates.
  repeated FeedUpdate updates = 1;
}

// Request payload for the get feed endpoint.
message GetFeedRequest {
  // ID of the system the feed is in.
  //
  // This is a URL parameter in the HTTP API.
  string system_id = 1;
  // ID of the feed.
  //
  // This is a URL parameter in the HTTP API.
  string feed_id = 2;
}

// Request payload for the list transfers endpoint.
message ListTransfersRequest {
  // ID of the system for which to list transfers.
  string system_id = 1;
}

// Response payload for the list transfers endpoint.
message ListTransfersReply {
  // List of transfers.
  repeated Transfer transfers = 1;
}

// The System resource.
message System {
  // ID of the system as specified in the install request.
  string id = 1;
  // Generic metadata about the system resource.
  Resource resource = 2;

  // Name of the system as specified in the system configuration file.
  string name = 4;

  // Enum describing the possible statuses of a system.
  enum Status {
    // Unknown status, included for protobuf reasons.
    UNKNOWN = 0;
    // The system is currently being installed through an asychronous install request.
    INSTALLING = 1;
    // The system was successfully installed and is now active.
    ACTIVE = 2;
    // The system was added through an asynchronous install request, but the install failed.
    INSTALL_FAILED = 3;
    // The system is currently being updated through an asynchronous update request.
    UPDATING = 4;
    // An asynchronous update of the system failed.
    UPDATE_FAILED = 5;
    // The system is in the process of being deleted through an asynchronous delete request.
    DELETING = 6;
  }
  // Status of the system.
  Status status = 5;

  ChildResources agencies = 6;
  ChildResources feeds = 7;
  ChildResources routes = 8;
  ChildResources stops = 9;
  ChildResources transfers = 10;

  // Reference is the reference type for the system resource.
  message Reference {
    string id = 1;
    Resource resource = 2;
  }
}

// The resource message contains generic metadata that applies to all resources.
message Resource {
  string path = 1;
  optional string href = 2;
}

// Description of a collection of child resources for a resource.
// This message and fields using this message exist to support API discoverability.
message ChildResources {
  // Number of child resources.
  int64 count = 1;
  // URL of the endpoint to list child resources.
  optional string href = 2;
}

// The Stop resource.
//
// This resource corresponds to the [stop type in the GTFS static
// specification](https://developers.google.com/transit/gtfs/reference#stopstxt).
// Most of the static fields in the resource come directly from the `stops.txt` table.
// Transiter adds some additional related fields (transfers, alerts, stop times)
//   and computed fields (service maps).
message Stop {
  // ID of the stop. This is the `stop_id` column in `stops.txt`.
  string id = 1;
  // Generic metadata about the stop resource.
  Resource resource = 2;
  // System corresponding to this stop.
  // This is the parent resource in Transiter's resource hierarchy.
  System.Reference system = 3;
  // Code of the stop. This is the `stop_code` column in `stops.txt`.
  optional string code = 4;
  // Name of the stop. This is the `stop_name` column in `stops.txt`.
  optional string name = 5;
  // Description of the stop. This is the `stop_desc` column in `stops.txt`.
  optional string description = 6;
  // Zone ID of the stop. This is the `zone_id` column in `stops.txt`.
  optional string zone_id = 7;
  // Latitude of the stop. This is the `stop_lat` column in `stops.txt`.
  optional double latitude = 8;
  // Longitude of the stop. This is the `stop_lon` column in `stops.txt`.
  optional double longitude = 9;
  // URL of a webpage about the stop. This is the `stop_url` column in `stops.txt`.
  optional string url = 10;

  // Enum describing the possible stop types
  enum Type {
    STOP = 0;
    STATION = 1;
    ENTRANCE_OR_EXIT = 2;
    GENERIC_NODE = 3;
    BOARDING_AREA = 4;
  }
  // Type of the stop. This is the `platform_type` column in `stops.txt`.
  Type type = 11;

  // Parent stop. This is determined using the `parent_station` column in `stops.txt`.
  optional Stop.Reference parent_stop = 12;
  // Child stops. This are determined using the `parent_station` column in `stops.txt`.
  repeated Stop.Reference child_stops = 13;
  // Timezone of the stop. This is the `stop_timezone` column in `stops.txt`.
  optional string timezone = 14;
  // If there is wheelchair boarding for this stop. This is the `wheelchair_boarding` column in `stops.txt`.
  optional bool wheelchair_boarding = 15;
  // Platform code of the stop. This is the `platform_code` column in `stops.txt`.
  optional string platform_code = 16;

  // Message describing the service maps view in stops.
  //
  // See the service maps documentation for more information on this
  // message and the associated field.
  message ServiceMap {
    // Config ID of the service map, as specified in the system configuration file.
    string config_id = 1;
    // List of routes which call at this stop.
    //
    // This list may be empty, in which case the stop has no service in the service map.
    repeated Route.Reference routes = 2;
  }
  // List of service maps for this stop.
  repeated ServiceMap service_maps = 17;

  // Active alerts for this stop.
  //
  // These are determined using the `informed_entity` field in
  // the [GTFS realtime alerts
  // message](https://developers.google.com/transit/gtfs-realtime/reference#message-alert).
  repeated Alert.Reference alerts = 18;

  // List of realtime stop times for this stop.
  //
  // A stop time is an event at which a trip calls at a stop.
  repeated StopTime stop_times = 19;

  // Transfers out of this stop.
  //
  // These are determined using the `from_stop_id` field in the GTFS static `transfers.txt` file.
  repeated Transfer transfers = 20;

  // Message describing a headsign rule.
  message HeadsignRule {
    // Stop the rule is for.
    Stop.Reference stop = 1;
    // Priority of the rule (lower is higher priority).
    int32 priority = 2;
    // NYCT track.
    optional string track = 3;
    // Headsign.
    string headsign = 4;
  }
  // List of headsign rules for this stop.
  repeated HeadsignRule headsign_rules = 21;

  // Reference is the reference type for the stop resource.
  message Reference {
    string id = 1;
    Resource resource = 2;
    System.Reference system = 3;
    optional string name = 4;
  }
}

// Message describing a realtime stop time.
//
// A stop time is an event in which a trip calls at a stop.
// This message corresponds to the [GTFS realtime `StopTimeUpdate`
// message](https://developers.google.com/transit/gtfs-realtime/reference#message-stoptimeupdate)
message StopTime {
  // The stop.
  Stop.Reference stop = 1;
  // The trip.
  Trip.Reference trip = 2;

  // Message describing the arrival or departure time of a stop time.
  // This corresponds to the [GTFS realtime `StopTimeEvent`
  // message](https://developers.google.com/transit/gtfs-realtime/reference#message-stoptimeevent).
  message EstimatedTime {
    optional int64 time = 1;
    optional int32 delay = 2;
    optional int32 uncertainty = 3;
  }
  // Arrival time.
  EstimatedTime arrival = 3;
  // Departure time.
  EstimatedTime departure = 4;
  // If this stop time is in the future.
  // This field is *not* based on the arrival or departure time.
  // Instead, a stop time is considered in the future if it appeared in the most recent
  // GTFS realtime feed for its trip.
  // When this stop time disappears from the trip, Transiter marks it as past and freezes
  // its data.
  bool future = 5;
  // Stop sequence.
  int32 stop_sequence = 6;
  // Headsign.
  optional string headsign = 7;
  // Track, from the NYCT realtime extension.
  optional string track = 8;
}

message Trip {
  string id = 1;
  // Generic metadata about the trip resource.
  Resource resource = 2;
  // Route corresponding to this trip.
  // This is the parent resource in Transiter's resource hierarchy.
  // It is determined using the `route_id` field in the GTFS realtime feed.
  Route.Reference route = 3;
  optional int64 started_at = 4;
  optional Vehicle.Reference vehicle = 5;
  bool direction_id = 6;

  repeated StopTime stop_times = 7;

  // Reference is the reference type for the trip resource.
  message Reference {
    string id = 1;
    Resource resource = 2;
    Route.Reference route = 3;
    Stop.Reference destination = 4;
    optional Vehicle.Reference vehicle = 5;
  }
}

message Vehicle {
  // Reference is the reference type for the vehicle resource.
  message Reference {
    string id = 1;
  }
}

// The Route resource.
//
// This resource corresponds to the [route type in the GTFS static
// specification](https://developers.google.com/transit/gtfs/reference#routestxt).
// Most of the fields in the resource come directly from the `routes.txt` table.
// Transiter adds some additional related fields (agency, alerts)
//   and computed fields (estimated headway, service maps).
message Route {
  // ID of the route. This is the `route_id` column in `routes.txt`.
  string id = 1;
  // Generic metadata about the route resource.
  Resource resource = 2;
  // System corresponding to this route.
  // This is the parent resource in Transiter's resource hierarchy.
  System.Reference system = 3;
  // Short name of the route. This is the `route_short_name` column in `routes.txt`.
  optional string short_name = 4;
  // Long name of the route. This is the `route_long_name` column in `routes.txt`.
  optional string long_name = 5;
  // Color of the route. This is the `route_color` column in `routes.txt`.
  string color = 6;
  // Text color of the route. This is the `route_text_color` column in `routes.txt`.
  string text_color = 7;
  // Description of the route. This is the `route_desc` column in `routes.txt`.
  optional string description = 8;
  // URL of a web page about the route. This is the `route_url` column in `routes.txt`.
  optional string url = 9;
  // Sort order of the route. This is the `route_sort_order` column in `routes.txt`.
  optional int32 sort_order = 10;

  // Enum describing possible policies for continuous pickup or drop-off.
  enum ContinuousPolicy {
    // Continuous pickup or drop-off allowed.
    ALLOWED = 0;
    // Continuous pickup or drop-off not allowed.
    NOT_ALLOWED = 1;
    // Must phone the agency to arrange continuous pickup or drop-off.
    PHONE_AGENCY = 2;
    // Must coordinate with driver to arrange continuous pickup or drop-off.
    COORDINATE_WITH_DRIVER = 3;
  }
  // Continuous pickup policy. This is the `continuous_pickup` column in `routes.txt`.
  ContinuousPolicy continuous_pickup = 11;
  // Continuous dropoff policy. This is the `continuous_dropoff` column in `routes.txt`.
  ContinuousPolicy continuous_drop_off = 12;

  // Enum describing possible route types.
  // This corresponds to possible values of the `route_type` column in `routes.txt`.
  enum Type {
    LIGHT_RAIL = 0;
    SUBWAY = 1;
    RAIL = 2;
    BUS = 3;
    FERRY = 4;
    CABLE_TRAM = 5;
    AERIAL_LIFT = 6;
    FUNICULAR = 7;
    TROLLEY_BUS = 11;
    MONORAIL = 12;
    UNKNOWN = 100;
  }
  // Type of the route. This is the `route_type` column in `routes.txt`.
  Type type = 13;

  // Agency this route is associated to.
  //
  // This is determined using the `agency_id` column in `routes.txt`.
  Agency.Reference agency = 14;

  // Active alerts for this route.
  //
  // These are determined using the `informed_entity` field in
  // the [GTFS realtime alerts
  // message](https://developers.google.com/transit/gtfs-realtime/reference#message-alert).
  repeated Alert.Reference alerts = 15;

  // An estimate of the interval of time between consecutive realtime trips, in seconds.
  //
  // If there is insufficient data to compute an estimate, the field will be empty.
  //
  // The estimate is computed as follows.
  // For each stop that has realtime trips for the route,
  //  the list of arrival times for those trips is examined.
  // The difference between consecutive arrival times is calculated.
  // If there are `N` trips, there will be `N-1` such arrival time diffs.
  // The estimated headway is the average of these diffs across
  // all stops.
  optional int32 estimated_headway = 16;

  // Message describing the service maps view in routes.
  //
  // See the service maps documentation for more information on this
  // message and the associated field.
  message ServiceMap {
    // Config ID of the service map, as specified in the system configuration file.
    string config_id = 1;
    // Ordered list of stop at which this route calls.
    //
    // This list may be empty, in which case the route has no service in the service map.
    repeated Stop.Reference stops = 2;
  }
  // List of service maps for this route.
  repeated ServiceMap service_maps = 17;

  // Reference is the reference type for the route resource.
  message Reference {
    string id = 1;
    Resource resource = 2;
    System.Reference system = 3;
    string color = 4;
  }
}

// The feed resource.
//
// Each feed is defined in the system configuration file.
// Feeds are included in the public API because there are non-admin use-cases for this resource.
// For example, an app might publish the staleness of realtime data
//   by checking for the last succesful feed update.
//
// More detailed information on a feed -- its full configuration, and the
//   current status of its periodic updates -- can be retrieved through the admin API.
message Feed {
  // ID of the feed, as specified in the system configuration file.
  string id = 1;
  // Generic metadata about the feed resource.
  Resource resource = 2;
  // System corresponding to this feed.
  // This is the parent resource in Transiter's resource hierarchy.
  System.Reference system = 3;

  // Updates for this feed.
  ChildResources updates = 4;

  // Reference is the reference type for the feed resource.
  message Reference {
    string id = 1;
    Resource resource = 2;
    System.Reference system = 3;
  }
}

// The Agency resource.
//
// This resource corresponds to the [agency type in the GTFS static
// specification](https://developers.google.com/transit/gtfs/reference#agencytxt).
// Most of the fields in the resource come directly from the `agency.txt` table.
// Transiter adds some additional related fields (alerts).
message Agency {
  // ID of the agency. This is the `agency_id` column in `agency.txt`.
  string id = 1;
  // Generic metadata about the agency resource.
  Resource resource = 2;
  // System corresponding to this agency.
  // This is the parent resource in Transiter's resource hierarchy.
  System.Reference system = 3;
  // Name of the agency. This is the `agency_name` column in `agency.txt`.
  string name = 4;
  // URL of the agency. This is the `agency_url` column in `agency.txt`.
  string url = 5;
  // Timezone of the agency. This is the `agency_timezone` column in `agency.txt`.
  string timezone = 6;
  // Language of the agency. This is the `agency_lang` column in `agency.txt`.
  optional string language = 7;
  // Phone number of the agency. This is the `agency_phone` column in `agency.txt`.
  optional string phone = 8;
  // URL where tickets for the agency's services ban be bought.
  // This is the `agency_fare_url` column in `agency.txt`.
  optional string fare_url = 9;
  // Email address of the agency. This is the `agency_email` column in `agency.txt`.
  optional string email = 10;

  repeated Route.Reference routes = 11;

  // List of active alerts for the agency.
  //
  // These are determined using the `informed_entity` field in
  // the [GTFS realtime alerts
  // message](https://developers.google.com/transit/gtfs-realtime/reference#message-alert).
  repeated Alert.Reference alerts = 12;

  // Reference is the reference type for the agency resource.
  message Reference {
    string id = 1;
    Resource resource = 2;
    System.Reference system = 3;
    string name = 4;
  }
}

// The Alert resource.
//
// This resource corresponds to the [alert type in the GTFS realtime
// specification](https://developers.google.com/transit/gtfs-realtime/reference#message-alert).
//
// TODO; alphabetize the messages
message Alert {
  // ID of the alert. This corresponds to the [ID field in the feed entity
  // message](https://developers.google.com/transit/gtfs-realtime/reference#message-feedentity)
  // corresponding to the alert.
  string id = 1;
  // Generic metadata about the alert resource.
  Resource resource = 2;
  // System corresponding to this alert.
  // This is the parent resource in Transiter's resource hierarchy.
  System.Reference system = 3;

  // Cause is the same as the [cause enum in the GTFS realtime
  // specification](https://developers.google.com/transit/gtfs-realtime/reference#enum-cause),
  // except `UNKNOWN_CAUSE` has value 0 instead of 1 to satisfy proto3 requirements.
  enum Cause {
    UNKNOWN_CAUSE = 0;
    OTHER_CAUSE = 2;
    TECHNICAL_PROBLEM = 3;
    STRIKE = 4;
    DEMONSTRATION = 5;
    ACCIDENT = 6;
    HOLIDAY = 7;
    WEATHER = 8;
    MAINTENANCE = 9;
    CONSTRUCTION = 10;
    POLICE_ACTIVITY = 11;
    MEDICAL_EMERGENCY = 12;
  }
  // Cause of the alert. This corresponds to the `cause` field in the realtime alert message.
  Cause cause = 4;

  // Effect is the same as the [effect enum in the GTFS realtime
  // specification](https://developers.google.com/transit/gtfs-realtime/reference#enum-effect),
  // except `UNKNOWN_EFFECT` has value 0 instead of 1 to satisfy proto3 requirements.
  enum Effect {
    UNKNOWN_EFFECT = 0;
    NO_SERVICE = 1;
    REDUCED_SERVICE = 2;
    SIGNIFICANT_DELAYS = 3;
    DETOUR = 4;
    ADDITIONAL_SERVICE = 5;
    MODIFIED_SERVICE = 6;
    OTHER_EFFECT = 7;
    STOP_MOVED = 9;
    NO_EFFECT = 10;
    ACCESSIBILITY_ISSUE = 11;
  }
  // Effect of the alert. This corresponds to the `effect` field in the realtime alert message.
  Effect effect = 5;

  // The active period message describes a period when an alert is active.
  // It corresponds the the [time range message in the GTFS realtime
  // specification](https://developers.google.com/transit/gtfs-realtime/reference#message-timerange).
  message ActivePeriod {
    // Unix timestamp of the start time of the active period.
    // If not set, the alert be interpreted
    // as being always active up to the end time.
    optional int64 starts_at = 1;
    // Unix timestamp of the end time of the active period.
    // If not set, the alert be interpreted as being indefinitely active.
    optional int64 ends_at = 2;
  }
  // The current active period, if the alert is currently active.
  // If the alert is not active this is empty.
  optional ActivePeriod current_active_period = 6;
  // All active periods for this alert.
  // Transiter guarantees that these active periods have no overlap.
  repeated ActivePeriod all_active_periods = 7;

  // The text message describes an alert header/description/URL in a specified language.
  // It corresponds the the [translation message in the GTFS realtime
  // specification](https://developers.google.com/transit/gtfs-realtime/reference#message-translation).
  message Text {
    // Content of the text.
    string text = 1;
    // Language of this text.
    string language = 2;
  }
  // Header of the alert, in zero or more languages.
  // This corresponds to the `header_text` field in the realtime alert message.
  repeated Text header = 8;
  // Description of the alert, in zero or more languages.
  // This corresponds to the `description_text` field in the realtime alert message.
  repeated Text description = 9;
  // URL for additional information about the alert, in zero or more languages.
  // This corresponds to the `url` field in the realtime alert message.
  repeated Text url = 10;

  // TODO: add informed entites for the alert.

  // Reference is the reference type for the agency resource.
  message Reference {
    string id = 1;
    Resource resource = 2;
    System.Reference system = 3;
    Cause cause = 4;
    Effect effect = 5;
  }
}

message Transfer {
  // TODO: id, system, resource
  // Probably will use the pk of the DB row for the ID
  Stop.Reference from_stop = 4;
  Stop.Reference to_stop = 5;

  enum Type {
    RECOMMENDED = 0;
    TIMED = 1;
    REQUIRES_TIME = 2;
    NO_POSSIBLE = 3;
  }
  Type type = 6;

  optional int32 min_transfer_time = 7;
  optional int32 distance = 8;
}

// The feed update resource.
//
// Each feed update event
//   -- triggered manually though the admin API, or automatically by the scheduler --
// generates a feed update resource.
// This resource is updated as the feed update progresses.
// A background task in Transiter periodically garbage collects old updates.
message FeedUpdate {
  // ID of the feed update. This is the primary key of the associated Postgres
  // database row so it's actually globally unique.
  string id = 1;
  // Generic metadata about the feed update resource.
  Resource resource = 2;
  // Feed corresponding to this update.
  // This is the parent resource in Transiter's resource hierarchy.
  Feed.Reference feed = 3;

  // Unix timestamp of when the update started.
  int64 started_at = 4;
  // Whether the update has finished. If false, the update is still in progress.
  bool finished = 5;
  // Unix timestamp of when the update finished.
  // Only populated if the update is finished.
  optional int64 finished_at = 6;

  enum Result {
    // Finished succesfully.
    UPDATED = 0;
    // The update was skipped because the downloaded data was identical to the data for the last succesful update.
    NOT_NEEDED = 1;
    // Failed to download feed data.
    DOWNLOAD_ERROR = 2;
    // Feed data was empty.
    EMPTY_FEED = 3;
    // The feed configuration is invalid. This typically indicates a bug in Transiter because
    // the feed configuration is validated when the system is being installed.
    INVALID_FEED_CONFIG = 4;
    // The parser specified in the feed configuration is invalid.
    INVALID_PARSER = 5;
    // Failed to parse the feed data.
    // This means the feed data was corrupted or otherwise invalid.
    PARSE_ERROR = 6;
    // Failed to update the database using the new feed data.
    // This typically indicates a bug in Transiter or a transient error connecting to the database.
    UPDATE_ERROR = 7;
    // An internal unspecified error occured.
    INTERNAL_ERROR = 8;
  }
  // Result of the update.
  // Only populated if the update is finished.
  optional Result result = 7;
  // Number of bytes in the downloaded feed data.
  // Only populated if the update succesfully downloaded the data.
  optional int32 content_length = 8;
  // Hash of the downloaded feed data. This is used to skip updates
  // if the feed data hasn't changed.
  // Only populated if the update succesfully downloaded the data.
  optional string content_hash = 9;
  // Error message of the update.
  // Only populated if the update finished in an error
  optional string error_message = 10;
}